1. Field of the Invention
The present invention relates to a state detecting device for detecting possible damage to a sheet-like image recording medium such as a stimulable phosphor sheet, for example.
2. Description of the Related Art
There is known a radiation image information recording and reading system, or a so-called CR (Computed Radiography) system, which employs a stimulable phosphor which, when exposed to an applied radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet radiation, or the like), stores a part of the energy of the radiation, and, when subsequently exposed to applied stimulating light such as visible light, emits light in proportion to the intensity of the stored energy of the radiation. In the CR system, the radiation image information of a subject such as a human body is temporarily recorded as a latent image in a stimulable phosphor sheet that comprises a stimulable phosphor layer in the form of a sheet. Then, stimulating light such as a laser beam is applied to the stimulable phosphor sheet to cause the stimulable phosphor sheet to emit light representing the recorded radiation image information. The emitted light is photoelectrically read to produce an image signal. Based on the image signal, the radiation image information of the subject is outputted or reproduced as a visible image on a recording medium such as a photographic photosensitive medium or a display unit such as a CRT.
Various types of CR systems are known in the art. One known type of CR system comprises a radiation image information recording apparatus for recording the radiation image information of a subject on a stimulable phosphor sheet and a radiation image information reading apparatus, separate from the radiation image information recording apparatus, for reading the radiation image information from the stimulable phosphor sheet. In this CR system, a cassette storing a stimulable phosphor sheet is loaded into the radiation image information recording apparatus, which records radiation image information on the stimulable phosphor sheet, or a cassette storing a stimulable phosphor sheet which carries recorded radiation image information is loaded into the radiation image information reading apparatus, which reads the recorded radiation image information from the stimulable phosphor sheet.
When a cassette with a stimulable phosphor sheet stored therein is transferred between the radiation image information recording apparatus and the radiation image information reading apparatus, if the cassette accidentally drops or impinges on a hard object, the cassette itself or the stimulable phosphor sheet stored therein may be damaged due to the shock.
To solve the above problem, Japanese patent publication No. 58-33540 or Japanese utility model registration publication No. 2568931, for example, discloses a cassette having elastic corner members made of rubber or elastic plastic which are positioned on the respective corners for protecting the cassette against damage when the cassette drops on top of a hard object. The disclosed cassette is highly durable and reduces impact forces applied to a stimulable phosphor sheet therein.
However, if excessively large shocks are applied to the cassette or regions of the cassette other than the corners, the cassette itself may possibly be damaged, preventing the stored stimulable phosphor sheet from being removed, or the stimulable phosphor sheet stored in the cassette may possibly be damaged. Particularly, when subjected to such shocks, a stimulable phosphor sheet, which comprises a stimulable phosphor layer disposed on a hard support, is more likely to be damaged than a stimulable phosphor sheet that comprises a stimulable phosphor layer disposed on a flexible support.
When an attempt is made to record radiation image information on the stimulable phosphor sheet without the damage of a cassette or a stimulable phosphor sheet stored therein being noticed, then the radiation image information may not be recorded accurately. If recorded radiation image is to be read from a damaged stimulable phosphor sheet or a damaged cassette, then the radiation image information reading device may malfunction or the radiation image information may not be read accurately.